Holden Captiva 2009: How to test a fault with injectors

I have a 2009 Holden Captiva LX diesel with 155,000 km on it. I recently noticed that the oil level had increased over the full mark. A diesel injection specialist suggested a DPF burn at their workshop as we were having the DPF light come on regularly. Since then and completing an oil change the DPF light hasn't come on anywhere nearly as regularly and after completing another 3000 to 4000 km I have noticed the oil level starting to rise approx. 10 mm over the top full mark. I am thinking it may be the injectors. The car continues to run ok and I haven't seen any smoke coming from the exhaust. Is there any possible way to test the injectors as well as is there any know fault similar to this?